The ability to use an applied electrical voltage to control fluid flow and/or ionization of a fluid is desirable for a number of applications. Electrospinning is one method by which fluid flow is controlled via the application of an electrical voltage. In many electrospinning systems, a polar, polymer-containing liquid is fed to a tip of an emitting protrusion (e.g., a needle). Application of a sufficiently high voltage results in electrostatic repulsion within components of the liquid. The electrostatic repulsion counteracts the surface tension of the liquid, and a stream of liquid erupts from the surface. If the molecular cohesion of the liquid is sufficiently high, stream breakup does not occur, and a charged liquid jet is formed. Electrospinning systems can be useful, for example, for producing small scale fibers, including nanoscale fibers.
Electrospraying systems offer another example of the use of an electrical voltage to control fluid flow. Generally, in an electrospraying system, a voltage is applied to a liquid (usually free of polymer, in contrast to many electrospinning applications) to produce ions and/or small droplets of charged liquid. In many such electro spraying systems, when the liquid is fed to the tip of the emitting protrusion and the voltage is applied, varicose waves on the surface of the resulting liquid jet lead to the formation of small and highly charged liquid droplets, which are radially dispersed due to Coulomb repulsion.
While electrospinning and electrospraying are known in the art, most systems include a single emitting protrusion, for example, in the form of a single needle. Increasing the throughput of such systems while avoiding degradation in performance has proven to be difficult. Increasing the throughput from a single protrusion has resulted in modest improvement, but has been accompanied by deterioration of the spread in the properties of the emitted liquid (e.g., size, shape, and the like). Increasing throughput by utilizing large arrays with high protrusion density has proven to be challenging.